The early diagnosis and multimodal treatment of children with Wilms' tumors have vastly improved survival rates. However, severe malnutrition (PEM) and numerous complications and toxicity are often associated with the treatment. Malnutrition reduces the capacity to withstand aggressive treatment, increases susceptibility to opportunistic infections, depresses immune function and increases morbidity and mortality. The purpose of this study is to prospectively evaluate the benefits and complications of several modes of nutrition support (i.e., enteral nutrition, partial parenteral nutrition - PPN, peripheral nutrient infusion with enteral nutrition - and total parenteral nutrition - TPN, central nutrient infusion) in children (ages one to seven years) receiving multimodal treatment for Wilms' tumors, stages II-IV. Each regimen will be evaluated for its effectiveness in preventing or reversing PEM, maintaining or restoring immune competence, and obviating treatment modifications and complications. Children with stage II-IV Wilms' tumors who are considered malnourished at diagnosis will be randomized to receive either TPN or PPN throughout the period of irradiation. Nourished children with either stage IV or stage II/III and unfavorable histology Wilms' tumors will be randomized to receive either PPN or TPN throughout the six weeks of abdominal irradiation. Nourished children with stage II/III and favorable histology Wilms' tumors will receive either a comprehensive enteral nutrition program or PPN throughout the four weeks of intense treatment which includes abdominal irradiation. Thereafter, all children will receive a comprehensive enteral nutrition program to prevent subclinical PEM during 2, 3, or 4 drug chemotherapy maintenance programs. Nutritional state, immunological capacity, treatment modifications and complications will be evaluated at diagnosis and at 4, 6, 19, and 26 weeks during the initial, intense and maintenance periods.